Which is an example of a compound ? sand , gold , water , iodine

 Water

Explanation:  Compound is a substance which is formed by the linkage of different or same kind of atoms.

It is absically composed of two or more elements.

Thus out of the given options, sand is composed of Silica (Si) , gold (Au) is the single element, Iodine (I2) is an diatomic element itself.

Water is made up of  2 moles of hydroge and one mole of oxygen. Thus it will be considered as a compound.

explanation: it gains negative electrons, therefore becoming negatively charged. as charge cannot be created, nor destroyed, only transferred, this leaves the wool positive. now that they have opposite charges, the two items attract.

the dissolution of polymer can be thermodynamically described in 2 steps.